Repair of Rotor Blades

[Mike Schallmann]

I picked up a set of Rotordyne blades that were made some time ago. Apparently there was some problems in the mfg of some of these blades. In this particular set the trailing edge has delaminated approx 4' from the root. The length of the delamination is approx 16".

I know of one case where the owner of a set of these blades had the same problem - he fixed them --by carefully cleaning out the old bonding agent from the opening and using an epoxy (for alumunum) rebonding them --he has flown them for several years since then with no problems.

I was thinking of doing this to these blades --in addition I was going to add a line of rivets ,say on 3" centers down the trailing edge, using either countersunk or universal head-- what do you think.

In all other aspects these blades are perfect -there is no evidence of delamination anwhere else -from my examination it appears that the width of the glue joint at the trailing edge was insufficient to maintain closure--

These blades wont be used on my current gyro --they will be used on another lighter weight project that I am working on--

[BUD ONEAL]

Mike,
I had the same thing happen to me. We did'nt try to reglue them but added rivets about four inches apart. I don't have the blades but they are still flying as far as I know.

[Vance]

Mike, I have a brand new set of Rotodyne blades that I will sell for $1,000. I will be visiting Avondale soon so I could deliver them on my way through Buckeye. These blades were made by Joe Souza about a 18 months ago.

The proper bonding also takes controlled heat and pressure, in my opinion it is best to not learn the process on critical aircraft parts. Rivets are more secure, but they do cause a certain amount of drag.

Thank you, Vance

[Mike Schallmann]

Vance
Thanks for the offer on the blades -- but the ones I have are an "extra" set - I really dont need another set of blades

[John Stahl]

Vance
What size are the rotodyne blades?

[Harry_S.]

Mike;

The original Rotordynes were sold as kits...many years ago.

I assembled several kits. The skins...top and bottom, were riveted at the front spar with solid flush head rivets and the trailing edge were riveted with solid brazier head rivets. I don't recall the exact rivet spacing but as mentioned, 4" spacing along the *entire span* sounds good.

I flew these blades for years and were still on the gyro when I sold it. I really liked 'em...would spin up quickly and were real smooth fliers as well.

Edit...I forgot to mention...there was no bonding agent used. Just metal to metal.


Cheers :)

[Vance]

Hello John,

They are 8 inch chord 11 feet long. I also have the rotor head and hub bar, $2500 for the whole rotor system. I do not have a good way to crate them, so it is up to you. I would like to borrow them back when I get my rotor test stand finished, but that is not critical to the pruchase.

My blades are bonded with no rivets. I don't believe that any of the blades that Joe Souza made have delaminated. The challenges stemed from the previous builder who only made them for a short time.

I was mostly trying to help Mike out and pay for my trip to Avondale.

I am not headed through Montana until August and I am not even sure of that, but I particularly like Missoula.

Thank you, Vance

[John Stahl]

Vance
The blades are too big for my needs. They are a good buy.

If and when you come to Missoula give me a call (I'm in the phone book) I will take you Fly Fishing in my ponds. The trout weigh between 5 to 8lbs. the largest caught in this pond weighed 17lbs was 37" long.

[Vance]

Thank you John, That is a very generous offer, Vance

[Doug Riley]

Rotordynes went through a collapse in quality during Laszlo's ownership. His blades were noted for de-laminating.

You can't assure a really reliable long-term bond without some rigorous surface prep. There's a chemical wash and primer. He skipped some part of this prep. The only way you could right this wrong using only glue would be to peel them completely apart, then clean and prep the surfaces.

A number of people have fixed Laszlo/Rotordynes by riveting them. The rivets should be aircraft solid rivets, not Pop rivets. Counter-sunk rivets are OK as long as the skin is thick enough so that the countersink doesn't go all the way through. Gyro blades generally don't use counter-sunk rivets, though.

I must admit that the whole concept of a shade-tree salvage job on something this critical scares me. I wouldn't do it.

[Mike Schallmann]

Doug
I understand your concerns -and I realize that a great deal of prep is necessary to secure a good bond-- I dont consider my repairs to "shade tree
" in the slightest -I have a fully equiupped shop and have an extensive experience in working with composites as well as metal and wood.

I also understand that I could have split the blades open and totally rebonded them --but then there is greater possibility of damaging the skins-- so the " glue and rivet " concept was formulated --


My main reason for asking the question in the first place was to learn if others had done this and what there results had been. I know the rivets would work --on my Bensen blades they are totally held together with rivets--

BTW --I really do appreciate all of the input I have recieved

[eddie1]

I bought a set of Rotordynes in 1998. Should I be concerned about the quality of the bonds.

Thanks for any info.

[C. Beaty]

Normal prebond surface prep for aluminum consists of a caustic soda cleaning followed by immersion in a chromic acid solution. The aluminum oxide film that forms instantly when aluminum is exposed to air is replaced by a chromate interface.

A light phosphoric acid anodizing is also good prep for bonding.

Aluminum’s affinity for oxygen is the reason it can’t be soft soldered or welded without some kind of shielding method that excludes oxygen.

Aluminum can be soft soldered nicely by heating until a puddle of solder forms and then scrubbing off the oxide through the puddle with a wire brush. The solder puddle excludes oxygen.

There was at one time a soldering iron for making electrical connections to aluminum with soft solder. There was a wire brush at the tip of the soldering iron that was driven ultrasonically. The brush scrubbed away the oxide and the puddle of molten solder provided the shielding.

Epoxy will of course cling to an abraded aluminum surface through mechanical interlocking. But that’s not bonding.

***

And Harry, perhaps you were thinking of Rotorhawk blades. To the best of my recollection, Rotordynes have always been wrap around bonded blades ever since the originator, Art Weillage began offering them in the 1960s.

Pete Johnson used to relate how he had a set of Rotordynes that outperformed all other Rotordynes. He had a set that had apparently slipped while in the bonding fixture; the spar wasn’t jammed all the way forward, leaving a less blunt leading edge.

[Passin' Thru]

Yep, they screwed up the bonding fixture and made the best flying set of blades I ever owned! :D

[Doug Riley]

Eddie:

Maybe. I think that Ladiszlao Supuch was the owner of Rotordyne who skimped on the process. Tracy Hansen bought the design from him and re-instituted the original bonding method. Blades made during Tracy's tenure are good.

[NoWingsAttached]

I crashed a set of Rotordynes. they hit they dirt at 45mph Ground speed and they did not delaminate. How about that for stick-to-it-ive-ness? I still have em in my back yard. I'll post photos if you don't believe me.

[eddie1]

Thanks Doug.

I guess I will dig a little deeper. Has the green anodizing finish always been used with Rotordynes?

Ed.

[NoWingsAttached]

Green? I guess I always thought of mine as "Champagne". Kind of a Gold color.